Injection moulding articles made of metallocene polypropylene

ABSTRACT

Homopolymers of propylene or copolymers of propylene with C 2 14 C 10 -alk-1-enes, which polymers are obtainable by polymerization of the corresponding monomers using metallocene catalysts are used for producing moldings such as injection-molded articles.

The present invention relates to the use of homopolymers of propylene orcopolymers of propylene with C₂-C₁₀-alk-1-enes, which polymers areobtainable by polymerization of the corresponding monomers usingmetallocene catalysts, for producing moldings, preferably hollow bodies,in particular injection-molded articles.

Plastics, in particular olefin polymers, are processed into moldingsusing the injection molding technique.

However, such moldings, or the polymers on which they are based, havedisadvantages.

Moldings having high transparency, for example made of random copolymersof propylene with other olefins, usually have unsatisfactory stiffness,expressed by the E modulus in accordance with ASTM D882.

On the other hand, moldings having a high stiffness, for example made ofhomopolymers of propylene, generally have insufficient transparency,measured in accordance with ASTM D1003.

Many of the currently available polyolefins which are employed ininjection molding also have unsatisfactory organoleptic properties(unpleasant odor and/or taste of the finished article).

It is an object of the present invention to develop polymers whichcombine high transparency with, at the same time, good stiffness andwhich additionally have a low odor and/or taste (good organolepticproperties) and a low proportion of xylene-soluble material, preferablyless than 1.5% by weight.

We have found that this object is achieved by the use of homopolymers ofpropylene or copolymers of propylene with C₂-C₁₀-alk-1-enes, whichpolymers are obtainable by polymerization of the corresponding monomersusing metallocene catalysts, for producing moldings and injection-moldedarticles as defined in the claims.

The propylene polymers according to the present invention are propylenehomopolymers or copolymers of propylene and an alk-1-ene or a pluralityof alk-1-enes selected from the group consisting of ethylene, 1-butene,1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene and4-methyl-1-pentene, or mixtures of these polymers, where the mixingratios are not critical. For the purposes of the present invention,copolymers are generally random copolymers.

The propylene homopolymers are essentially isotactic.

The homopolymers of propylene or copolymers of propylene withC₂-C₁₀-alk-1-enes, having the above-described composition and structure,are obtained by polymerization of the corresponding monomers usingmetallocene catalysts. Hereinafter, such propylene polymers are referredto as “propylene homopolymers and copolymers according to the presentinvention”.

For the purposes of the present invention, metallocene catalysts arematerials which are generally formed by combining a transition metalcompound or a plurality of transition metal compounds, preferably oftitanium, zirconium or hafnium, which contain at least one ligand whichis, in the widest sense, a derivative of the cyclopentadienyl ligand,with an activator, also referred to as cocatalyst or compound capable offorming metallocenium ions, and generally display polymerizationactivity toward the monomers described. Such catalysts are described,for example, in EP-A 0 545 303, EP-A 0 576 970 and EP-A 0 582 194.

Well suited catalysts are described, for example, in WO 97/19980, page3, line 16 to page 11, line 17.

Very particularly preferred metallocene components of the catalystsystems are

rac-dimethylsilylenebis(2-methylbenzindenyl)zirconium dichloride

rac-dimethylsilylenebis(2-ethylbenzindenyl)zirconium dichloride

rac-dimethylsilylenebis(2-methylindenyl)zirconium dichloride

rac-dimethylsilylenebis(2,4-dimethylindenyl)zirconium dichloride

rac-dimethylsilylenebis(2,4,7-trimethylindenyl)zirconium dichloride

rac-dimethylsilylenebis(2-methyl-4-isopropylindenyl)zirconium dichloride

rac-dimethylsilylenebis(2-methyl-4,6-diisopropylindenyl)zirconiumdichloride

rac-dimethylsilylenebis(2-methyl-4-phenylindenyl)zirconium dichloride

rac-dimethylsilylenebis(2-ethyl-4-phenylindenyl)zirconium dichloride

rac-dimethylsilylenebis(2-methyl-4-naphthylindenyl)zirconium dichloride

rac-ethylenebis(2-methylbenzindenyl)zirconium dichloride

rac-ethylenebis(2-ethylbenzindenyl)zirconium dichloride

rac-ethylenebis(2-methylindenyl)zirconium dichloride

rac-ethylenebis(2,4-dimethylindenyl)zirconium dichloride

rac-ethylenebis(2,4,7-trimethylindenyl)zirconium dichloride

rac-ethylene(2-methyl-4-isopropylindenyl)zirconium dichloride

rac-ethylenebis(2-methyl-4,6-diisopropylindenyl)zirconium dichloride

rac-ethylenebis(2-methyl-4-phenylindenyl)zirconium dichloride

rac-ethylenebis(2-ethyl-4-phenylindenyl)zirconium dichloride

rac-ethylenebis(2-methyl-4-naphthylindenyl)zirconium dichloride

The preparation of the polypropylene polymers can be carried out in thecustomary reactors used for the polymerization of olefins, eitherbatchwise or preferably continuously. Suitable reactors are, inter alia,continuously operated stirred vessels or loop reactors; it is alsopossible, if desired, to use a plurality of stirred vessels or loopreactors connected in series. The polymerization reactions can becarried out in the gas phase, in suspension, in liquid and insupercritical monomers or in inert solvents.

The polymerization conditions are in themselves not critical. Pressuresof from 100 to 350,000 kPa, preferably from 100 to 250,000 and inparticular from 100 to 100,000 kPa, and temperatures of from 0 to 400°C., preferably from 20 to 250° C. and in particular from 50 to 100° C.,have been found to be useful.

The mean molecular weight of the polymers can be controlled by means ofthe methods customary in polymerization technology, for example byintroduction of molecular weight regulators such as hydrogen which leadsto a reduction in the molecular weight of the polymer or by variation ofthe polymerization temperature, where high polymerization temperaturesusually likewise lead to reduced molecular weights.

The propylene homopolymers and copolymers according to the presentinvention generally have a melt flow rate (MFR) measured at 230° C. anda load of 2.16 kg in accordance with DIN 53735 in the range from 10 to100 g/10 min, preferably in the range from 40 to 80 g/10 min and inparticular in the range from 50 to 65 g/10 min.

The molecular weight distribution of the propylene homopolymers andcopolymers according to the present invention Mw/Mn, determined by meansof GPC at 140° C. in 1,2,4-trichlorobenzene relative to a polypropylenestandard, is generally in the range from 1.2 to 3.0, preferably from 1.2to 2.5.

The molecular weight Mw, the molecular weight distribution Mw/Mn and, inparticular, the MFR can also be adjusted by peroxidically initiateddegradation of a starting polymer, advantageously in an extruder. Thismethod is known to those skilled in the art.

The propylene homopolymers according to the present invention generallyhave a melting point, determined by differential scanning calorimetry(DSC) in the range from 80° C. to 170° C., preferably in the range from135° C. to 165° C. and in particular in the range from 140° C. to 165°C.

The copolymers according to the invention of propylene withC₂-C₁₀-alk-1-enes generally have a melting point, determined bydifferential scanning calorimetry (DSC) (heating rate: 20° C./min.), inthe range from 60° C. to 160° C., preferably in the range from 80 to150° C. and in particular in the range from 100° C. to 150° C.

The pentad content mmmm, in other words the isotacticity, of thehomopolymers according to the present invention, determined by ¹³C-NMRspectroscopy, is usually in the range from 60% to 99%, preferably in therange from 80% to 98%.

The proportion of xylene-soluble material in the propylene homopolymersand copolymers according to the present invention is usually less than1.5% by weight, preferably less than 1.0% by weight.

The proportion of xylene-soluble material X_(S) was determined asfollows:

500 ml of distilled xylene (isomer mixture) were placed in a 1 literthree-neck flask fitted with stirrer, reflux condenser and thermometerand were heated to 100° C. At this temperature, the polymer wasintroduced, the mixture was subsequently heated to the boiling point ofxylene and was refluxed for 60 minutes. Subsequently, the supply of heatwas stopped, the mixture was cooled to 5° C. over a period of 20 minutesusing a cooling bath and was then reheated to 20° C. This temperaturewas held for 30 minutes. The polymer which precipitated was filtered offand exactly 100 ml of the filtrate were placed in a previously tared 250ml one-neck flask. The solvent was then removed on a rotary evaporator.The residue which was left was subsequently dried for 2 hours in avacuum drying oven at 80° C./200 torr. After cooling, the flask wasreweighed. $X_{S} = \frac{g \times 500 \times 100}{G \times V}$

X_(S)=proportion of xylene-soluble material in %

g=amount found

G=weight of product sample

V=volume of filtrate used

The chemically bound proportion of comonomer in the, preferably random,copolymers according to the present invention of propylene withC₂-C₁₀-alk-1-enes, measured by ¹³C-NMR spectroscopy, is generally in therange from 0.001 to 35 mol %, preferably in the range from 0.01 to 15mol %, based on the copolymers. Suitable C₂-C₁₀-alkenes are, inparticular, ethylene, 1-butene and mixtures thereof.

A well suited propylene polymer is the homopolypropylene NOVOLEN® M NX50081 from Targor GmbH (previously BASF Aktiengesellschaft).

The moldings according to the present invention (injection-moldedarticles) are generally produced using the customary injection moldingprocesses known to those skilled in the art.

The E modulus of the propylene homopolymers and copolymers according tothe present invention, measured in a tensile test in accordance with ISO527, is generally in the range from 1300 to 7500, preferably in therange from 1500 to 7500.

The haze, as a complementary value to transparency, determined inaccordance with ASTM D 1003, is less than 10%, preferably less than 8%,for the propylene homopolymers and copolymers according to the presentinvention.

The injection-molded articles according to the present invention canfurther comprise the customary thermoplastic additives in the customaryamounts. Possible additives are antistatic agents, lubricants such asfatty acid amides, for example erucamide, stabilizers, neutralizingagents such as calcium stearate, pigments and also inorganic fillerssuch as talc, aluminum oxide, aluminum sulfate, barium sulfate, calciummagnesium carbonate, silicon dioxide, titanium dioxide and glass fibersor else organic fillers such as polyesters, polystyrene, polyamide andhalogenated organic polymers.

Other preferred additives are nucleating agents such as talc, alkalimetal salts or aluminum salts of carboxylic and alkylaryl acids, certainpolymers such as polyvinylcyclohexane or polycyclopentene andpolyhydroxy compounds such as sorbitol derivatives. Particularpreference is given to sorbitol derivatives.

The propylene homopolymers and copolymers according to the presentinvention are well suited to producing moldings, preferably hollowbodies, in particular injection-molded articles for a variety ofapplications, as described by way of example in the following.

The propylene homopolymers and copolymers according to the presentinvention are suitable for uses (applications)

in the audio/video/computer sector

eg. CD/CD-ROM packaging, cassette bodies (audio/video), boxes for floppydisks and tapes;

in the medical sector

eg. Petri dishes, cuvettes/blood analysis tubes, pipettes, disposablepipette tips, drug packaging, in particular vials or lids, syringebarrels, milk pumps, packaging for tablets, mouthpieces for inhalers;

in dairy and food packaging

eg. yoghurt tubs, dessert tubs, cheese packaging, pate packaging,gourmet food tubs, containers for single portions, trays for prepackagedmeals, spice containers;

in the household article sector

eg. drinking cups, containers for food, Ferrero®, Tupperware®, microwaveapplications, catering, blow-molded containers, water softening filters,brewery filters, clothes hangers, insulated drink containers, babybottles, lids for baby bottles, parts for dummies;

in the office supplies sector

eg. trays, filing boxes, magazine racks, box files, drawing requisites;

in the cosmetics packaging sector

eg. ointment containers, caps, cartridges, boxes for wet wipes, pots,roll-on deodorant containers (ball and housing);

for closures, caps, lids of all sorts; laundry detergent packaging

eg. dosing balls;

in the sanitary sector

eg. toothbrush cases, toothpaste containers such as tubes anddispensers, beakers, brush bodies, bathroom shelves, bathroom furniture,mirror cabinets, toilet seats, hotel soap dispensers;

in the electrical appliance sector

eg. coffee machine housings, sightglasses for coffee machines or waterboilers, lids for egg cookers, refrigeration appliance internalcomponents such as vegetable compartments, optical waveguides eg. inautomobiles and passenger cars, clothes irons, water containers such aslids for water boilers, lamp covers;

in the storage container and transport container sector

eg. containers for screws, containers for tools, sightglasses,containers for transporting animals, jewelry and gift packaging such asSwatch® packaging, baskets, wall holders;

in the writing implements sector

eg. bodies of pens;

in the toy sector

eg. packaging for playing cards, containers for storing toys eg. forLego® building blocks;

in the laboratory requisites sector

eg. measuring cups, measuring cylinders, laboratory flasks eg. foraggressive substances, buckets.

Furthermore, the propylene homopolymers and copolymers according to thepresent invention are well suited for producing moldings, preferablyinjection-molded articles

eg. cartridges, clips and rings, eg. for curtains, boards for computerchips, protective casings for computer chip boards, cases;

in the tool sector

eg. tool handles;

in the motor vehicle sector

eg. covers for interior lights, substitutes for glass, polycarbonate orpolystyrene;

in the furniture sector, preferably outdoor furniture,

eg. transparent, colored or non-colored garden furniture.

We claim:
 1. Injection-molded CD packaging or injection-molded CD-ROMpackaging comprising an essentially isotactic homopolymer of propyleneor a copolymer of propylene with C₂-C₁₀-alk-1-enes, which polymer isobtained by polymerization of the corresponding monomers usingmetallocene catalysts, wherein the homopolymer of propylene has (1) aMelt Flow Rate of 40-80 g/10 min. (measured at 230° C. with a load of2.16 kg in accordance with DIN 53735); (2) a molecular weightdistribution of 1.2 to 2.5 (Mw/Mn); (3) a melting point of 140-165° C.(DSC); (4) a pentad content mmmm of 80% to 98% (determined by 13C-NMR);(5) a xylene-soluble content of less than 1% by weight; (6) an E modulusof 1500 to 7000 (measured in a tensile test by ISO 527); and (7) a hazeof less than 8% (determined by ASTMD 1003), and wherein the copolymer ofpropylene has (1) a Melt Flow Rate of 40-80 g/10 min.; (2) a meltingpoint of 100° to 150° C. (DSC); (3) a Mw/Mn ratio of 1.2 to 2.5; (4) axylene-soluble content of less than 1% by weight; (5) a chemically boundproportion of comonomer in the range of 0.01 to 15 mol %; (6) an Emodulus, measured in a tensile test, in the range of from 1500 to 7500(tensile test in accordance with ISO 527); and (7) haze of less than 8%(determined in accordance with ASTM D 1003).
 2. The injection-moldedpackaging of claim 1, wherein the copolymer of propylene is used forsaid packaging.
 3. The injection-molded packaging of claim 1, whereinthe homopolymer of propylene is used for said packaging.
 4. A processfor preparing CD packaging or CD-ROM packaging wherein propylene or amonomer mixture of propylene and at least one further C₂-C₁₀-alk-1-eneis polymerized by metallocene catalysts and the resulting essentiallyisotactic homopolymer of propylene or copolymer of propylene withC₂-C₁₀-alk-1-enes is injection molded to said CD packaging or CD-ROMpackaging, wherein the homopolymer of propylene has (1) a Melt Flow Rateof 40-80 g/10 min. (measured at 230° C. with a load of 2.16 kg inaccordance with DIN 53735); (2) a molecular weight distribution of 1.2to 2.5 (Mw/Mn); (3) a melting point of 140-165° C. (DSC); (4) a pentadcontent mmmm of 80% to 98% (determined by 13C-NMR); (5) a xylene-solublecontent of less than 1% by weight; (6) an E modulus of 1500 to 7000(measured in a tensile test by ISO 527); and (7) a haze of less than 8%(determined by ASTMD 1003), and wherein the copolymer of propylene has(1) a Melt Flow Rate of 40-80 g/10 min.; (2) a melting point of 100° to150° C. (DSC); (3) a Mw/Mn ratio of 1.2 to 2.5; (4) a xylene-solublecontent of less than 1% by weight; (5) a chemically bound proportion ofcomonomer in the range of 0.01 to 15 mol %; (6) an E modulus, measuredin a tensile test, in the range of from 1500 to 7500 (tensile test inaccordance with ISO 527); and (7) haze of less than 8% (determined inaccordance with ASTM D 1003).
 5. The process of claim 4, wherein thehomopolymer of propylene is used for said packaging.
 6. The process ofclaim 4, wherein a copolymer of propylene is used for said packaging.